Salt-resistant hydrophobically modified copolymer nanostructures as viscosity increasing agents for enhanced oil recovery

ABSTRACT

A hydrophobically modified copolymer nanostructure includes a first monomer and a second monomer. The first monomer is a hydrophilic monomer. The second monomer is a non-ionic short-chain hydrophobic monomer. The first monomer and the second monomer form a microblock structure, forming nanoparticles. The microblock structure is the hydrophobically modified copolymer nanostructure.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to an Iran patentapplication having serial number 139450140003003488 filed on Jun. 22,2015, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to oil extraction and, moreparticularly, to polymer flooding processes for oil recovery. Also itrelates to other applications such as cosmetics, coatings and drillingfluids.

BACKGROUND

In the context of oil extraction, oil reservoirs can be fractured,thereby trapping oil even upon completion of classical oil recoveryprocesses, such as water flooding, gas injection and in-situ combustion.There are known processes, sometimes referred to as “secondary” and“tertiary” oil recovery, aimed at recovering portions of this trappedoil. One such process is polymer flooding. This is a flooding processthat uses natural polymers, such as xanthan and starch, and syntheticpolymers, for example, polyacrylamide (PAM) and partially hydrolyzedpolyacrylamide (HPAM). The polymer can increase the viscosity of theinjected water. This can increase sweep efficiency due to the improvedmobility ratio, and can reduce the total volume of water required toreach the residual oil saturation. Use of PAM and HPAM, identifiedabove, are known in the field of polymer flooding, generally forcontrolling the mobility ratio of water to oil. PAM and HPAM canincrease the water viscosity, which hinders a phenomenon known as “waterfingering” and, instead, operates to push the oil forward or to thefront for retrieval.

The above-described operations of PAM and HPAM result from the highmolecular weight of the polymers and the repulsion between the negativecharges along the polymer chain of HPAM, each being based on maximumchain extension. A limitation of traditional polymer flooding, however,is that the polymer chains exhibit degradations during the floodingprocess. Examples include thermal degradation, as well as mechanical,salinity, shear and biological degradations of polymer chains during theflooding process.

In addition, shearing and heating in wellbores and reservoirs oftendecrease the polymer viscosity. Polymer solutions, as any non-Newtonianfluid, conform to the power law, including viscosity, shear rate,consistency index, and flow behavior index. The polymer solutionviscosity is thus easily calculated under any shear rate based on thedetermined consistency and flow behavior indexes. As is understood inthe art, the consistency index increases with increasing polymerconcentration, but decreases with increasing temperature. On the otherhand, the flow behavior index decreases with increasing polymerconcentration, and slightly increases at high temperature. Therefore, itshould be understood that a higher HPAM concentration leads to higherviscosities, and polymer viscosity is reduced at a higher shear rate andtemperature.

SUMMARY

Disclosed aspects include a salt-resistant hydrophobically modifiedcopolymer nanostructure, and a process for producing it. Features andadvantages can include salt-resistance and being neutral non-ionic.Related features include use of the disclosed salt-resistanthydrophobically modified copolymer nanostructure as a viscosityincreasing agent for enhanced oil recovery. As will be appreciated fromthis disclosure, salt-resistant hydrophobically modified copolymernanostructure according to this disclosure can protect water-solublepolymers from rapid degradations and mechanical shear stresses, both insurface facilities and near wellbores through porous media inunderground reservoirs. Accordingly, polymer flooding with thehydrophobically modified copolymer nanostructures of the instantapplication can provide, among other features, increased oil recovery.

A disclosed method of synthesizing the salt-resistant hydrophobicallymodified copolymer nanostructure can include a first phase, a secondphase and a third phase. In an aspect, the first phase can includeproducing an inverse nano-emulsion, by adding a solution of asurfactant, a hydrophilic monomer and an osmotic agent to an organicsolvent under mechanical stirring. The second phase can includeintroducing the hydrophobic monomer to nano-emulsion, and then adding aninitiator of a reaction that forms the hydrophobically modifiedcopolymer nanostructure as a hydrophilic-hydrophobic copolymer having amicroblock nanostructure. The third phase can include recovering thehydrophobically modified copolymer nanostructure from the organicsolvent.

In an aspect, the hydrophilic monomer can include acrylamide, acrylicacid and their derivative, the hydrophobic monomer includes non-ionicshort-chain monomer such as divinylbenzene, 4-methylstyrene,vinylcyclohexane, 4-vinylphenol, 4-vinylpyridine, 2-vinylnaphthalene,styrene and 1-vinylnaphthalene, the osmotic agent can include a sodiumhydroxide solution. In another aspect, a surfactant with HLB of 2-6 isrequired. The organic solvent with high enough boiling point caninclude, for example, cyclohexane, benzene and heptane. In an aspect,the initiator can include an oil-soluble initiator such asazobisisobutyronitrile (AIBN), benzoyl peroxide (BPO) and lauroylperoxide (LPO).

Organic Solvents Boiling point (° C.) Benzene 80.1 cyclohexane 80.74toluene 110.6 chlorobenzene 131 carbon tetrachloride 76.72 heptane 98.42

The second phase can include, according to various aspects, apolymerization of the non-ionic short-chain hydrophobic monomer to formhydrophobic oligoradicals, at an organic phase. The polymerization canproceed until its concentration in organic phase saturates and theformed hydrophobic oligoradicals become insoluble in organic phase. Thehydrophobic oligoradicals may then be repulsed by organic phase andstart to accumulate on the micelles. In an aspect, the polymerizationprocess can also proceed inside the micelles. These operations canresult in a copolymerization of hydrophilic monomer inside the micellesand the hydrophobic monomer outside the micelles. The describedcopolymerization processes can continue to form the hydrophobicallymodified copolymer nanostructure as the hydrophobic-hydrophilic polymerhaving a microblock copolymer structure. In the describedcopolymerization processes, hydrophobic monomers can be grafted with thehydrophilic open end chains, to produce the salt-resistanthydrophobically modified copolymer nanostructure as a nanostructure ofblock copolymers.

The third phase can include separation of the hydrophobically modifiedcopolymer nanostructure, by precipitation from the described solution.In an aspect, precipitation can include rinsing the hydrophobicallymodified copolymer nanostructure by methanol or acetone several times toseparate the unreacted monomers and unreacted surfactant from thesalt-resistant hydrophobically modified copolymer nanostructure. Inaddition, the synthesized salt-resistant hydrophobically modified can befurther dried under vacuum.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of the subject technology are set forth in the appended claims.However, for purpose of explanation, several implementations of thesubject technology are set forth in the following figures.

FIG. 1 illustrates a process for synthesizing a salt-resistanthydrophobically modified copolymer nanostructure as aviscosity-increasing agent for enhanced oil recovery, according to apreferred implementation of the instant application.

FIG. 2 illustrates a Fourier Transform Infra-Red (FT-IR) spectrum of thepolyacrylamide and a preferred copolymer, according to animplementation.

FIG. 3 illustrates a nuclear magnetic resonance (HNMR) spectrum of thepolyacrylamide and a preferred copolymer, according to animplementation.

FIG. 4 shows a schematic of the two possible structures for thehydrophobically modified copolymer nanostructure.

FIGS. 5A and 5B illustrate field-emission scanning electron microscopy(FE-SEM) images of the copolymer.

FIG. 6 illustrates a fluorescent spectrum of the copolymer HM-PAM.

FIGS. 7A and 7B show, respectively, a size distribution of the particlesof the hydrophobically modified copolymer nanostructure andpolyacrylamide based on dynamic light scattering (DLS) method.

FIG. 8 illustrates a rate of change of reduced viscosity of thehydrophobically modified copolymer nanostructure versus concentration atroom temperature.

FIGS. 9A and 9B show a rate of change of viscosity of thehydrophobically modified copolymer nanostructure and HPAM versus shearrate at different salinity at room temperature.

FIG. 10 illustrates a rate of change of viscosity of the solutions ofhydrophobically modified copolymer nanostructure and HPAM at differentsalinity and fixed shear rate at room temperature.

FIGS. 11A and 11B illustrate, respectively, a viscosity of thehydrophobically modified copolymer nanostructure and HPAM at fixed shearrate and different temperature and salinities.

FIG. 12 illustrates a rate of change of viscosity of the solutions ofhydrophobically modified copolymer nanostructure versus shear rate atdifferent divalent cations (Mg²⁺).

DETAILED DESCRIPTION

In the following detailed description, various examples are presented toprovide a thorough understanding of inventive concepts, and variousaspects thereof that are set forth by this disclosure. However, uponreading the present disclosure, it may become apparent to persons ofskill that various inventive concepts and aspects thereof may bepracticed without one or more details shown in the examples. In otherinstances, well known procedures, operations and materials have beendescribed at a relatively high-level, without detail, to avoidunnecessarily obscuring description of inventive concepts and aspectsthereof.

In traditional polymer flooding, a high viscosity polymeric solution,including hydrophilic polymer (for example, HPAM and PAM) and water, isinjected into underground reservoirs by high viscosity pumps. Theinjecting can be after water flooding and its fingering phenomenon. Thissolution is injected to propagate through the water phase and controlthe mobility ratio of water to oil. However, as described above.

The chain extension approach leads to one of the greatest disadvantagesof using PAM and HPAM in oil reservoirs. For example, when polyvalentsalts are used in oilfield brine solutions, negative charges areextended from each other along the polymer chain by interaction withcations in the solution. The polymer chains no longer extend fully,which can cause the solution to have decreased viscosity due to theion-dipole interaction between the salt cations and the oxygen atoms inpolyacrylamide molecules. The strong ion-dipole interaction between thedivalent cations, Ca²⁺ and Mg²⁺ and the amide group because of highercharge densities than Nat, weakens the bond strengths of NaH and C═Obonds. These phenomena, in combination with various mechanical factorscan lead to the chemical degradation of polymer molecules and a decreasein the polymer solution viscosity.

Examples of such mechanical factors include, first, the use of hugepumps and other equipment to inject the viscous polymer solution intothe underground reservoirs. Second, mechanical, thermal and bacterialdamages, as well as surface absorption, can result in the particulardisadvantages in the use of hydrophilic polymers, such as PAM, HPAM,TVP, and xanthan during the traditional polymer flooding. Third, anincrease in the water viscosity in undesired directions before reachingthe remaining oil areas, and use of excessive polymers to increaseviscosity in heavy oil reservoirs are other limitations of thistraditional polymer flooding technique and approach.

The present application discloses a salt-resistant hydrophobicallymodified copolymer nanostructure, which after oil recovery byconventional water flooding, can be injected into underground reservoirsby low viscosity pumps, such as water pumps, as is understood in theart. Benefits of the salt-resistant hydrophobically modified copolymernanostructure can include not only resistance to increased levels ofwater salinity, but also increasing the viscosity in presence ofmonovalent and divalent ions.

Regarding particle size, the average size of the pores in the porousmedia encountered in secondary and tertiary oil recover application isabout 1 micrometer. Synthesized particles normally should be about oneorder of magnitude less than this size to permit adequate flow-throughand prevent plugging. Therefore, assuming a porosity of micrometer,synthesized particles should be no more than 100 nanometers. Inaddition, even smaller particles can assist in obtaining a stablesuspension of particles in water.

FIG. 1 illustrates an example process 100 for synthesizing ahydrophobically modified copolymer nanostructure 110 according tovarious aspects. For brevity of description, the hydrophobicallymodified copolymer nanostructure will be alternatively referenced as“hydrophobically modified HM-PAM.” According to various aspects, thehydrophobically modified copolymer nanostructure 110 can exhibit, amongother features, significant resistance to salt. Therefore,hydrophobically modified copolymer nanostructure 110 will bealternatively referenced as “salt-resistant hydrophobically modifiedHM-PAM” 110. The salt-resistant hydrophobically modified HM-PAM 110 inaccordance with various aspects disclosed herein can exhibitcharacteristics, additional to salt resistance that can make itadvantageous as a viscosity increasing agent for enhanced oil recovery.

The process 100 can be a modified inverse nano-emulsion process, definedaccording to concepts disclosed herein, for synthesizing salt-resistanthydrophobically modified HM-PAM 110, includes three phases 140, 142 and144. The process 100 can begin at the first phase 140 with synthesizinga nano-emulsion 112.

The first phase 140 can be a synthesizing of a nano-emulsion 112 thatincludes acrylamides, acrylic acid and their derivative 114, sodiumhydroxide 116, cyclohexane, benzene and heptane 118 and a surfactantwith HLB of 2-6 120.

The acrylamide, acrylic acid or their derivative 114 may be added to theosmotic agent (0.1M sodium hydroxide solution) 118. Then the organicsolvent 118 and the surfactant may be mixed in the reactor underhomogenizer. The produced nano-emulsion 112 may be stirred mechanicallyand degassed by an inert gas for 30 minutes in a three-neck flask. Thenano-emulsion is subsequently sent to the second phase 142.

The second phase 142 may include adding to the nano-emulsion 112 fromphase one 140, non-ionic short-chain hydrophobic monomer such asstyrene, divinylbenzene, 4-methylstyrene, vinylcyclohexane,4-vinylphenol, 4-vinylpyridine, 2-vinylnaphthalene and1-vinylnaphthalene 122, micelles 124 and organic solvent 126. Thenon-ionic short-chain hydrophobic monomer 122 is added to synthesizednano-emulsion 112 from first phase 140, while under mechanical stirringand degasification by an inert gas for another 30 minutes. Afterward,the reaction temperature may increase to 60° C. by a heater and theoil-soluble initiator 126, is added to the reactor. Theco-polymerization takes place for 3-4 hours at 60° C. and under constantmechanical stirring and degasification by an inert gas, forming thehydrophobic-hydrophilic copolymer, which is the HM-PAM 100. Since theinitiator 126 is an organic compound, the polymerization reaction startsat an organic, non-aqueous phase.

Referring to FIG. 1, as the polymerization of the non-ionic short-chainhydrophobic monomer 122 in organic phase proceeds, its concentration inorganic solvent 118 saturates and the formed hydrophobic (oligoradicals)becomes poor-soluble in organic solvent 118. Hydrophobic oligoradicalsmay be repulsed by organic solvent 118 and start to accumulate on themicelles. The polymerization process also proceeds inside the micelles124, which leads to copolymerization of hydrophilic monomer 118 insidethe micelles 124 and the hydrophobic monomer 122 outside the micelles124 and, further, to formation of the hydrophobic-hydrophilic blockcopolymer structure of the hydrophobically modified HM-PAM 110. Thethird phase 144 of the synthesis recovers the hydrophobically modifiedHM-PAM 110 from the solution.

The third phase 144 can include separation of the salt-resistanthydrophobically modified 110 from the solution by rinsing in methanol oracetone. The synthesized hydrophobically modified HM-PAM 110 inside thesolution can be precipitated by methanol or acetone. The salt-resistanthydrophobically modified HM-PAM nanostructure 110 can be rinsed bymethanol or acetone several times, and thereby separate out theunreacted monomers 114 and 116 and unreacted surfactant 120. Thesynthesized salt-resistant hydrophobically modified HM-PAM 110 can befurther dried under vacuum.

In contrast to the above-described methods and operations, known methodsfor producing hydrophobically modified copolymers can includepolymerizing hydrophilic monomer, and subsequently extending the chainwith polymerizing hydrophobic monomer at the reactive end of thehydrophilic chains. The result has susceptibility to temperaturedegradation, as well as mechanical, salinity, shear and biologicaldegradations of polymer chains during the flooding process.

FIG. 2 illustrates Fourier-Transform Infra-Red (FT-IR) spectra of thereactant and the synthesized copolymer nanostructure. Polyacrylamide(PAM) and copolymer (HM-PAM) spectra are shown. The peak at 3400 cm⁻¹ isamide group and the peak at 1660 cm⁻¹ is the carboxylic group in bothpolyacrylamide and the copolymer structures.

Characterization of the salt-resistant hydrophobically modified HM-PAMnanostructure properties pursuant to the present application can bedone, for example, by Dynamic light scattering (DLS), Fourier TransformInfra-red spectroscopy (RT-IR), Field-emission scanning electronmicroscopy (FE-SEM), nuclear magnetic resonance spectroscopy (NMR),Ubbelohde viscometer and rheometer.

FIG. 3 shows the Nuclear Magnetic Resonance (¹HNMR) spectrum. The HNMRwas done in D₂O. Different aromatic and aliphatic C—H peaks can be seen.Peak at 1.7 ppm relates to a —CH₂ group and the peak at 2.3 ppm is a—CH-group. It should be noted that the peak at 4.8 ppm is related to thesolvent.

According to FIG. 4, there are two different possible structures for thehydrophobically modified HM-PAM, which are: random structure andmicroblock structure. The microblock structure has a greater number ofmolecular interactions than the random structure. The microblockstructure therefore has increased viscosity at low concentration whencompared to the random structure. Accordingly, the reaction parametersdescribed above are configured to favor synthesizing the microblockstructure.

The salt-resistant hydrophobically modified copolymer nanostructure alsoshows fluorescence properties. FIG. 6 illustrates the fluorescencespectrum of the HM-PAM. The random structure has fluorescence emissionat 305 nm and the microblock structure has fluorescence emission at 361nm. As can be seen, the intensity of the fluorescent emission of themicroblock structure is twice the intensity of the random structure.This indicates the microblock structure being the dominant compositionin the hydrophobically modified HM-PAM nanostructure according to thisdisclosure.

FIGS. 5A and 5B show the morphology of the HM-PAM using a Field-EmissionScanning Electron Microscope (FE-SEM). FIG. 7 particle size distributionby a using a Dynamic Light Scattering (DLS). The results show that thespherical nanoparticles are approximately 70 nm in diameter. The nanometric size of the molecules enhances the solubility of the particles inwater, despite the high percentage of the hydrophobic monomer.

FIG. 8 illustrates the intrinsic viscosity of the copolymer and thenon-modified viscosity of the PAM versus the concentration. To calculatethe intrinsic viscosity, Equation (1) below was used:

η_(red) =[η]+k _(H)[η]² C _(p)   Eqn. (1)

Where η_(red) is reduced viscosity, η is the intrinsic viscosity, k_(H)is the Huggins constant and C_(p) is the polymer concentration.

As can be seen in FIG. 8, the polyacrylamide's reduced viscosity islinear. However, in case of the salt-resistant hydrophobically modifiedHM-PAM, this correlation spikes at a specific concentration (criticalconcentration). At the critical concentration, the hydrophobicintra-actions of the hydrophobic groups change to molecularinteractions, which lead to sudden increase in viscosity of thecopolymer. According to rheological measurements, increasing thehydrophobia content up to 10 mol % makes an enhancement in viscosity ofHM-PAM copolymers due to hydrophobic association in aqueous solutionswith formation of hydrophobic micro-domains, which become morepronounced above the critical concentration of copolymer in water.

Reference is now made to FIGS. 9A-12. As mentioned hereinabove, use ofPAM and HPAM in polymer flooding processes is known. These polymersincrease the water viscosity, hindering water-fingering phenomena and,as long as these properties remain intact, operate to push the oilforward or to the front for retrieval. PAM and HPAM employ maximum chainextension to obtain high molecular weight of the polymers, and repulsionbetween the negative charges along the polymer chain. The chainextension approach, though, creates inherent vulnerability todegradations during flooding processes. For example, when polyvalentsalts are used in oilfield brine solutions, negative charges areextended from each other along the polymer chain by interaction withcations in the solution. The polymer chains, as a result, no longerextend fully. This can cause the solution to have decreased viscositydue to strong ion-dipole interaction between the salt cations and theoxygen atoms in polyacrylamide molecules. The strong ion-dipoleinteraction between the divalent cations, Ca²⁺ and Mg²⁺ and the amidegroup can establish higher charge densities than Nat, and thereby weakenthe bond strengths of NaH and C═O bonds. The weakened bond strengths cancause chemical degradation of polymer molecules and an associateddecrease of the polymer solution viscosity. On the other hand, the flowbehavior index decreases with increasing polymer concentration, andslightly increases at high temperature. Therefore, it should beunderstood that a higher HPAM concentration leads to higher viscosities,and polymer viscosity is reduced at a higher shear rate (FIG. 9A) andtemperature (FIGS. 11A and 11B).

Synthesized salt-resistant hydrophobically modified HM-PAMnanostructures according to disclosed concepts and aspects thereof donot contain anionic groups. Therefore, the viscosity of the HM-PAMbecomes stable as the salinity and the temperature of the medium change.This makes the present hydrophobically modified copolymer nanostructureadvantageous for use in flooding process in enhanced oil recovery, sinceionic groups could cover the ionic carboxylate groups in HPAM, andtherefore aggregates this polymer. At higher concentrations, it couldlead to polymer precipitation and sudden decrease in viscosity of theHPAM. FIG. 10 illustrates the comparison between the change of viscosityof the HPAM and HM-PAM versus the water salinity. As can be seen, thepresence of salt ions increases the polarity of the water, which causesincrease in molecular interactions in the HM-PAM, therefore increase inviscosity of the HM-PAM copolymer nanostructures.

In addition, shearing and heating in wellbores and reservoirs oftendecrease the polymer viscosity. Polymer solutions, as any non-Newtonianfluid, conform to the power law, including viscosity, shear rate,consistency index, and flow behavior index. The polymer solutionviscosity is thus easily calculated under any shear rate based on thedetermined consistency and flow behavior indexes as with any fluid.

FIG. 12 shows a rate of change of viscosity of the solutions ofhydrophobically modified copolymer nanostructure versus shear rate atdifferent divalent cations (Mg²⁺). In case of conventional polymers suchas HPAM, in hard water (with high contents of Ca²⁺ and Mg²⁺)precipitation may occur due to complexing ability of the carboxylategroups of HPAM and resulting in a rapid decreasing of viscosity. Manyoil fields inject seawater as injection water which contains thesedivalent ions. Furthermore, during EOR process, the polymer will be incontact with the underground water containing monovalent and divalentions, which have a great influence on the properties of polymers inaqueous solution. However, hydrophobically modified copolymernanostructures, contrary to most of conventional polymers, not only arestable in the presence of monovalent and divalent ions, but also asignificant enhancement of viscosity may be observed with increasing thedivalent ions.

Other implementations are contemplated.

Except as stated immediately above, nothing that has been stated orillustrated is intended or should be interpreted to cause a dedicationof any component, step, feature, object, benefit, advantage, orequivalent to the public, regardless of whether it is or is not recitedin the claims.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”or any other variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises a list of elements does not include only those elements butmay include other elements not expressly listed or inherent to suchprocess, method, article, or apparatus. An element proceeded by “a” or“an” does not, without further constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises the element.

The Abstract of the Disclosure is provided to allow the reader toquickly ascertain the nature of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims. In addition, in theforegoing Detailed Description, it can be seen that various features aregrouped together in various implementations. This is for purposes ofstreamlining the disclosure, and is not to be interpreted as reflectingan intention that the claimed implementations require more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed implementation. Thus, the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

What is claimed is:
 1. A hydrophobically modified copolymernanostructure, comprising: a first monomer, the first monomer beinghydrophilic monomer; and a second monomer, the second monomer beingnon-ionic short-chain hydrophobic monomer, wherein the first monomer andthe second monomer form a microblock structure, forming nanoparticles,the microblock structure being the hydrophobically modified copolymernanostructure.
 2. The hydrophobically modified copolymer nanostructureof claim 1, wherein the nanostructure is salt-resistant.
 3. Thehydrophobically modified copolymer nanostructure of claim 1, wherein thenanostructure is neutral.
 4. The hydrophobically modified copolymernanostructure of claim 1, wherein the nanostructure is non-ionic.
 5. Thehydrophobically modified copolymer nanostructure of claim 1, wherein thenanostructure forms spherical nanoparticles, having a nanometric size,wherein the nanometric size is a diameter of approximately 70 nm.
 6. Thehydrophobically modified copolymer nanostructure of claim 1, wherein thenanostructure forms spherical nanoparticles, having a nanometric size,wherein the nanometric size enhances a solubility of the sphericalnano-particles in water.
 7. The hydrophobically modified copolymernanostructure of claim 1, wherein the hydrophobically modified copolymernanostructure does not contain anionic groups.
 8. A method of producinga hydrophobically modified copolymer nanostructure, the methodcomprising; adding a hydrophilic monomer, an osmotic agent and asurfactant to an organic solvent to produce a nano-emulsion; adding ahydrophobic monomer to the produced nano-emulsion and an oil-solubleinitiator to start a reaction and produce the hydrophobically modifiedcopolymer; and recovering the hydrophobically modified copolymernanostructure from the organic solvent.
 9. The method of claim 8,wherein producing the nano-emulsion includes adding the hydrophilicmonomer, osmotic agent and the surfactant to the organic solvent andstirring the mixture.
 10. The method of claim 9, wherein the osmoticagent includes a sodium hydroxide solution.
 11. The method of claim 9,wherein the surfactant includes a surfactant with HLB of 2-6.
 12. Themethod of claim 9, wherein: the organic solvent includes cyclohexanebenzene or heptane having a high boiling point.
 13. The method of claim9, wherein: the initiator includes an oil-soluble initiator, and theoil-soluble initiator includes azobisisobutyronitrile (AIBN), benzoylperoxide (BPO) or lauroyl peroxide (LPO).
 14. The method of claim 9,wherein: the osmotic agent includes a sodium hydroxide solution, theorganic solvent includes cyclohexane, benzene or heptane, the initiatorincludes an oil-soluble initiator, and the oil-soluble initiatorincludes benzoyl peroxide (BPO), lauroyl peroxide (LPO) orazobisisobutyronitrile (AIBN).
 15. The method of claim 8, furthercomprising polymerizing the hydrophobic monomer, wherein thepolymerizing includes adding the hydrophobic monomer to thenano-emulsion while under mechanical stirring, to form micelles, andthen adding the initiator of the reaction that synthesize thehydrophobically modified copolymer nanostructure as ahydrophobic/hydrophilic polymer having a microblock copolymer structure.16. The method of claim 15, wherein producing the nano-emulsion includesadding the hydrophilic monomer, the osmotic agent and the surfactant tothe organic solvent and stirring the mixture.
 17. The method of claim16, wherein: the osmotic agent includes a sodium hydroxide solution, theorganic solvent includes cyclohexane, benzene or heptane, the initiatorincludes benzoyl peroxide (BPO), lauroyl peroxide (LPO) orazobisisobutyronitrile (AIBN).
 18. The method of claim 8, whereinpolymerizing leaves unreacted monomers and unreacted surfactant, andwherein recovering the hydrophobically modified copolymer nanostructurecomprising rinsing the hydrophobically modified copolymer nanostructureby methanol to separate unreacted monomers and unreacted surfactant fromthe hydrophobically modified copolymer nanostructure.
 19. The method ofclaim 18, wherein recovering the hydrophobically modified copolymernanostructure further comprises drying the hydrophobically modifiedcopolymer nanostructure under vacuum.